Hyperhidrosis: Hyperhidrosis refers to profuse perspiration (excessive sweating) beyond the body's thermoregulatory needs. It is believed that an estimated 2-3% of Americans suffer from excessive sweating of the underarms (axillary hyperhidrosis) or the palms and soles of the feet (palmoplantar hyperhidrosis). For the purpose of discussion that follows, palmar hyperhidrosis (excessive sweating of the palms) will be stressed. Sweaty palms disorder is embarrassing, can hamper business interactions and cause social anxiety. Severe cases of palmar hyperhidrosis also have serious consequences, prohibiting people suffering from such a disorder to shake hands, lift any objects or work in professions that require contact with electricity.
Primary palmar hyperhidrosis is caused by overactivity of the sympathetic nervous systems, largely triggered by emotional stresses including anxiety, nervousness, anger and fear. Sympathetic nervous system is one of two major parts of the autonomic nervous system, the other being the parasympathetic system. In cases of palmar hyperhidrosis, the stellate ganglion and the first, second, third and forth thoracic ganglia of the sympathetic nerve chain are believed to play the major role in the abnormal signal generation to sweat glands of the palms.
There are various treatments available for palmar hyperhidrosis. Aluminum chloride is used in antiperspirants. However, patients suffered from hyperhidrosis require antiperspirants in high concentration to effectively treat the symptoms of the condition. Anticholinergic drugs have direct effect on sympathetic nervous systems although they have side effects. Botulinum injection on affected area may block neural control of sweat glands. However, such a treatment is expensive and short-term, with patients requiring to receive injection every 6 to 12 months.
Removal or destruction of sweat gland is one surgical option available for hyperhidrosis although such a treatment has many side effects. Endoscopic transthoracic sympathectomy (ETS), a minimally invasive surgical procedure, involves resection or clamping of the thoracic ganglion on the main sympathetic chain. Particularly, an en bloc ablation by laser vaporization of the T2 ganglion has proven to yield a permanent therapeutic effect for palmar hyperhidrosis. However, ablation of the targeted nerve cluster has a host of complications, including compensatory sweating, bradycardia, hypersensitive to light, lack of norepinephrine and acetylcholine, and possibly nerve regeneration. Clamping of the thoracic ganglion is intended to permit the reversal of the ablation procedure so as to minimize the aforementioned complications. However, it has shown that effective clamping also causes irreversible damages to the nerve, and patients continue to suffer similar side effects such as compensatory hyperhidrosis.
Electrical stimulation of the sympathetic nerve chain has been proposed to treat hyperhidrosis. The principle behind such approach involves disruption and modulation of hyperactive neuronal circuit transmission at specific sites in the sympathetic nerve chain. The procedure is also said to minimizes or possibly eliminate the complications from ETS. Currently, electrical stimulation of the nerve is usually carried out by surgically implanting a generator in the vicinity of the targeted nerve cluster, and then applying electrical modulation to the nerve through electrodes that are connected to the generator by lead. Conventional stimulation device, however, bears significant shortcomings. For example, the implantable generator requires a battery or power source, which means the size of the device cannot be too small. Also, an extension lead, containing electric wire, is attached to the generator and carries the electric pulses to the electrode that is attached to the nerves or tissues. This lead is undesirable as it may tangle with or disturb the nearby organs. If damaged, a leak and possibly more severe complications may occur as a result.
It is therefore the goal of the present invention to provide a treatment method for palmar hyperhidrosis by employing a miniature, battery-less stimulator that requires no extension lead.
Raynaud's phenomenon: Raynaud's phenomenon is a disorder of the blood vessels, usually in the fingers and toes. It is a condition in which cold temperature or emotional stress causes blood vessel spasms that block blood circulation to the fingers and toes. Specifically, Raynaud's phenomenon is a hyperactivation of the sympathetic nervous system causing extreme vasoconstriction of the peripheral blood vessels, lead to tissue hypoxia. Typical symptoms are pain within the affected extremities, discoloration, and sensations of cold and/or numbness. The disorder can be distressing and in severe cases, dangerous when someone with Raynaud's is placed in cold climate.
Treatment for Raynaud's phenomenon may include prescription medicines such as nifedipine or diltiazem, though it has the usual side effects of headache, flushing, and ankle edema. An ETS can be performed by ablating the nerves that signal the blood vessels of the fingertips to constrict. But complications common to ETS would also occur.
Cerebral ischemia: cerebral ischemia is a medical disorder where there is insufficient blood flow to the brain to meet metabolic demand. Typically ischemia occurs when one of the arteries that brings blood to a part of the brain is blocked by a blood clot or a cholesterol plague. The resulting lack of oxygen or cerebral hypoxia leads to death of brain cells or ischemic stroke. Cerebral ischemia is a leading cause of adult disability in the United States, killing nearly 150,000 people each year.
Tissue plasminogen activator (TPA) is an effective medication that lyses a clot and possibly restores blood circulation to the affected area of the brain. However, administering TPA has a very limited time window of only 3-4 hours. TPA also may not be suitable for patients with certain conditions, such as tendency to bleed, heart problems or diabetics, because there is the potential risk of serious brain bleed. Surgery, such as carotid endarterectomy, may also be performed on patients suffering from brain ischemia. The procedure aims to unlock carotid arteries, which supply blood to the brain, that have accumulated plaque or fat buildup in them. However, the inherent dangers of such surgical procedure prompt other safer and less invasive approach for the treatment of cerebral ischemia
Asthma: Asthma is a chronic lung disorder that inflames and narrows the airways. The inner walls of an asthmatic's airways are swollen or inflamed. This swelling and inflammation makes the airways extremely sensitive to irritations and increases one's susceptibility to an allergic reaction.
Most asthma medications work by relaxing bronchospasm. Treatment is usually with an inhaled short-acting beta-2 agonist and oral corticosteroids. Side effects such as insomnia, anxiety, increased heart rate and tremor occur in some patients taking asthmatic medications.
Hypertension: Hypertension is a medical condition in which the blood pressure in the arteries is elevated. An elevation of blood pressure increases the risk of developing cardiac disease, renal disease, atherosclerosis or arteriosclerosis, eye damage and stroke. It is estimated that hypertension affects approximately one in three adults in the U.S., —73 million people—clearly a serious public health problem.
Abnormally elevated sympathetic nerve activity is found to contribute to the progression of hypertension and renal disease. Therefore, hypertension, renal and heart failure can be treated by reducing the sympathetic efferent or afferent nerve activity of the kidneys. Medication such as rennin-angiotensin system inhibitors, calcium channel blockers or diuretics have been used to treat hypertension.
The causes of the prevalent diseases discussed herein can all be related to abnormal activities of the sympathetic nerve chain. Therefore, novel methods of treating these diseases are presented to reduce the side-effects associated with the conventional approaches.